The present invention relates to a spreadable bar for eyeglass frames provided with a spring hinge.
As it is known the resiliency in the horizontal plane of the eyeglass frame bars, as provided with spring hinges, permits a more rational and convenient use of the eyeglasses to be obtained, in such a way as to be able of fitting any users, the rod being effective to provide a slight and suitable pressure on the user head, thereby assuring a stable and positive engaging together with the bearing on the nose of the nose-piece of the eyeglass frame.
More specifically, the eyeglass makers tend to supply eyeglasses provided with such a bar, by using working devices and methods effective to afford this possibility, or resiliency.
There are substantially known two systems for obtaining eyeglass frame bars effective to be spread apart in a horizontal plane. The first is to practically construct the bar in two portions and engage these portions by means of leaf springs, in such a way as to permit the bar end portion to swing.
The second system consists of applying a spring biassed hinge on the bar, more precisely in the zone whereof adjoining the eyeglass frame. In these hinges there is provided an inner guiding portion, provided with a projected end which projects from the hinge and is pivoted on the eyeglass frame.
The first system is generally inferior to the second, because of constructional difficulties and the poor aesthetic aspect of the bar which seemingly is broken.
Based on the concept of the second system, that is to spring bias the hinge connecting the bar to the eyeglass frame, several constructional solutions have been devised and, generally, each eyeglass maker adopts a solution of his own for his eyeglasses.
However all these constructional approaches are based on the same system including a coil spring housed in the bar hinge fixed to the eyeglass frame bar, said spring being enclosed in the projecting guiding portion of the hinge, and, more precisely, it is housed between the inner end of said guiding portion and a fixed abutment of the bar, which abutment penetrates the cavity of the guiding portion housing said spring. Accordingly, as the bar is spread apart or opened, it provides, because of its contacting movement with the bar hinging bearing, a pressing on said spring and this latter, in turn, will provide a reaction force tending to cause the bar to be reset.
All of the approaches relating spring biassed hinges characteristically are completely made of metal, such as, for example, stainless steel or metal alloys.
A main drawback of the known spring biassed hinge eyeglasses is the great wear of the metal portions due to repeated opening and closing movements of the bars. Moreover the coil spring itself, made of steel, tends to loose its efficacy. Furthermore the known spring biassed eyeglass bar hinges, being made of a metal material, have a comparatively high weight which, as it is well known, is rather annoying for the user, because of the pressure exercised by the eyeglasses on the blood-vessels and veins of the user's nose thereby, after a time, the blood circulation of the user is slackened with consequent headaches, fatiguing of the eyes and the like.
Furthermore, in the case in which stainless steel is used, great manufacturing difficulties arise, because of the material itself, and, in addition, it is necessary to carry out plating operations. In the case in which metal alloys are used, oxidation phenomena and colour changes occurs, which are antiaesthetic, due to the corrosion of the sweat depositing on said metal parts. This depositing, furthermore, favours the depositing of dust and the like, thereby dirt builds up abrading the metal portions of the hinge. This fact makes the bar movements difficult and, after a some degree of abrading, clearances are formed negatively affecting the operation of the hinge springs.
A further drawback of the metal hinges is that the metal parts can cause wounds in the case of impacts, accidents and falls, in particular in the case of children.
These drawbacks, from one side, are favoured by the presence of metal parts and, on the other side, are frequently related to the rigidity of said metal parts, since these latter do not afford the possibility of causing the bar to swing in the vertical plane and even, in the case of high swinging stresses in the vertical plane, the bar or the supporting portion whereof breaks, with consequent woundings as due to the impacts of these broken portions on the user's face.